Process of bleaching.



UNITED STATES PATENT oniuoE.

ROESSLER & HAssiZA 'FRIEDRICH LpDWIGisbg MIDT, OF CHARLOTTENBURG.GERMANY. AsstGNoR TO THE HER CHEMICAL COMPANY. A

CORPORATION OF NEW YORK.

PROCESS OF BLEACHING.

No Drawing. Original application filed January 25. 1910, Serial No.filed January 9, 1911.

To all H'lwm it may won/cm Be it known that I, Fnn-znuuru LL'owioScnmirr. a citizen of the German Empire. residing at Charlottenburg, insaid German lmpire, have invented certain new and useful ImprovementsinflProcesses of Bleaching, of which the following is a specification.

This invention relates to an improved process of bleaching by means ofborates containing active oxygen in the presence of compounds ofmagnesium, of the alkaline earth metals and of zinc.

, Sodium perborate possesses the property of giving off its oxygenrather rapid y in water at a temperature as low as 50 C. This is adisadvantage in the applicationof sodium perborate as a bleaching agent,1n-' asmuch as the washing and bleaching process can only properly beginat a higher temperature, so that a large proportion of the oxygen willbe driven off and its effect lost before the efficient temperature isattained. In view of this fact, the discovery that magnesium perborateevolves its oxygen at a hi her temperature represented an advance.

It is known that mixtures of sodium per borate and a magnesium salt inequivalent proportions can be employed for bleaching, instead of puremagnesium perborate. In this case the magnesium perborate is formed fromthe sodium perborate and the magnesium salt by double decomposition. Theproportions which are used in the latter process are such that the wholeof the sodium perborate is decomposed by the magnesium salt. To thisextent the latter process only differs from that with magnesiumperborate in the fact that the magnesium perborate is produced by thesaiddouble decomposition just before the bleachmg occurs.

While the employment of magnesium perborate for bleaching purposesrepresents an advance as regards the bleaching effect.

owing to the greater stability of the magnesium perborate under boiling,yet, on the other hand, its high price and some other shortcomingsmilitate against its wide employment.

I have now found that it is possible to obtain the effect of greaterresistance to boiling with the cheap sodium pcrborate and with otheralkali metal perboratcs containing active oxygen, by adding certainsubstances to the same. To these substances be- Specification of LettersPatent.

Patented Sept. 28. 191?.

540,044. Divided Serial No. 601,695.

and this application long also the salts of magnesimu and their theabove-mentioned processaccording to which sodium perbi'i'rate iscompletehfdecomposed by equivalent proportions of magnesium salt.

I have found that it is not necessary to add to the alkali metalperborate so much magnesiumcompound that the whole bleachrg process iscarried out with magnesium perborate, that is to say. that all thesodium perborate is decomposed by the magnesium salt. ()n the contrary,I have found that it is possible to attain the said effect of greaterresistance to boiling with only very small proportions of an addition ofa magnesium compound. For example, the addition ofa fraction ofamolecular proportion suliices to attain a very distinct effect, as willup pear from the following: A one per cent. solution of sodiumperborate, heated to -80 C. was found after a few minutes to have losthalf of its active oxvgen and after twenty-live minutes only 10 percent. of the oxygen remained. When one-sixth of a molecular proportionof magnesium sulfate is added to one molecular proportion of sodiumperborate, dissolved toa one per cent. solution, about 98 per cent. ofthe ac the oxygen remainsafter twenty-five minutes heatin to 7080. Whenunder the same conditions one-twelfth of a molecular proportion ofmagnesium sulfate is added, the effect of this-addition is that aftertwenty -five minutes heating to the same temperature, about per cent. ofthe oxygen remains. The addition of one-sixtieth of a molecularproportion of magnesium sulfate under exactly the same conditions hasthe effect that about 70 per cent. of the oxygen remains after thesameperiod. It follows from these examples that in order'to attain ahigher resistance to boiling, it is not necessary to convert the alkalimetal perborate completely into magnesium perborate, but, on thecontrary. a very small molecular proportion of magnesium salt suflices.This action of less than equivalent proportions of magnesium salt wasnot to be foreseen, for inl. the new process, in which the greaterpdrtion of the sodium perborate remains unaltered in solution, thenatural assumption would therefore be that this unaltered sodiumperborate would split the oxygen just as readily as do ordinarysolutions of sodium perborate.

The new process utilizing only small quantities of magnesium salt is ofspecial importance on account of its technical advantage over the knownprocess using either ready prepared magnesium perborate or freshlyformed magnesium perborate. Both magnesium perborate and the magnesiumborate into which theforrner becomes congifted after the bleachingaction are insolue. liquor a considerable quantity of such magnesiumprecipitate, which, owing to the large quantity present, has adetrimental effeet and is diiiicult to remove from the bleachedgoods. Byusing smaller quantities of'magnesium salt, far less of this troublesomeprecipitate has to be dealt with,

- and the less the quantity of magnesium salt and the remaining oxygenbeinf: n'l'easured after twenty-live minutes: The addition of one-sixthof a molecular proportion of chlorid of calcium is found to make thesolution stable up to about 87 per cent, while one-fiftieth of amolecular proportion of chlorid of *alciuni is found to give astabilityof about 50 per cent. One-lifteenth of a. molecular proportionof Strontium chlorid gives about 90 per cent. stability, oue-' twelfthof a molecular proportion of barium chlorid about 50 per cent.stability.

The following is an example of the bleaching process as carried outby-borates containing active oxygen: 200 kilograms of cotton, which isfreed in the well-known manner by boiling it with caustic soda from thepectin compounds, is treated with a solu tion' of 2,000 liters of watercontaining 10 kilos of caustic soda, 5 kilos of soap, 1.5

kilos of sodiumperborate, and 0.2 kilo of crystallized magnesiumsulfate, for about live hours in an open vessel, or for from three tofour hours under pressure at a temperature of 110 0., under continuousstirring of the mass. After cooling the bleached cotton is separatedfrom the bleaching liquor, washed and dried.

There is therefore in the bleaching perborate crystallized calciumchlorid, or 0.2? kilo or r talliaed strontium chlorid, or 0.25 kilo ctallized barium chlorid. The quantities or these substances can beincreased or creased. in the place of caustic soda, other alkalinesubstances, as, for instance, or Turkey-red oil, can be used. In placecotton, other vegetable fibers, such as liner can be treated withadvantage by the innproved bleaching substances, and also test tilefabrics. I

The fixing effect of the said substances J5 applies not only to sodiumperhorate, but also to the other borates containing active oxygen, whichcan be obtained by crystall zation or by mixing or melting. The cobtained also applies to mixtures it with other substances not having a.coat action. The said fixing substances added to the active borates andhandled or mixture. of both of them, ready iror use an be placed uponthe market, or the procedure may be such that they are added just beforeuse 0 during use. i

It is not even necessary that the salts or bases ha ring an action inthe described sense shall be of the ordinary kind; for example, thepersalts and peroxids oi' the same will serve the purpose.

I wish to heunderstood that the term is also to embraceother boratescontaining active oxygen, as for stance pcrborax and such boratcs,containins, active oxygen, as manufactured by the process covered U. S.Patent No. 1,006,798 issued to me.

Having thus describedmy invention, 1 claim has new and desire to secureby Letters Patent:

1. The process herein described of Wash ing and bleaching fibers bymeans of a pen borate, which consists in applying; the same to thefibers in the presence, of a soluble inorgauic compound of mamiesiumin-a less than equivalent proportion.

52. The process herein described of washing and bleaching fibers bymeans a pen borate which consists in applying the some to the fibers inthe presence of a. soluble. 3" organic compound of an alkali earth me.in a less than equivalent proportion.

In testimony,that I claim the foregoingas my invention, l have signed myname in presence of two subscribing witnesses.

FRlEDRICll LUDWIG SCHMIDT.

Witnesses:

Rmnnonn Gunner, v Max h'lxn'rsclnui.

